Lars magnus ericsson



Patented Dec. 20, I898.

L. M. ERICSSON. MICROPHONE CONTAINING GBANULAR CARBON FORRETAINING MATEBIALU.

IN POSITION.

(Application filed Apr 6, 1898.)

(N0 Model.)

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m: poms pzvsas 1:0,: mm'aumm, WASHINGTON n. c.

- UNITED STATES L ARS MAGNUS ERIOSSON, OF STOOKI'IOLM, SYVEDEN, ASSIGNOR TO. THE AKTIEBOLAGET Ii. M. ERICSSON & COMPANY, OF SAME PLACE.

- MiCRGF'riGh'E CONlfAlNlNG GHANU IQAR CARBON FOR RETAINING MATERIAL lN POSITION.

SPECIFICATION forming part of Letters Patent No. 616,186, dated. December 20, 1898.

Application filed April 6. 1898. Serial No. 676,676. No model.) 1

To all whom it may concern.-

Be itknown that I, LABS MAeNUs ERIGSSON, manufacturer, a subject of the King of Sweden and Norway, and a resident of Thnlegatan 5, Stockholm, in the Kingdom of Sweden, have invented certain new and useful Improvein attempting to produce a good carbon microphone containing granular carbon has been to invent an arrangement for retaining the granular material securely in place without exerting an undue and varying pressure on the diaphragm. This invention relates to an arrangement by means of which the difficulty referred to has been overcome. The arran gement consists in inclosing the mass of granular carbon by an elastiomaterial which is made to exert a uniform (not varying) pressure'en the diaphragm, while taking part in its vibrations, and thus at the same time damping the latter to a certain extent.

In the accompanying drawings, Figure 1 shows a microphone in a vertical section and Fig. 2 in a plan' view. Figs. 3, 4., 5, and (3 show details of the spring arrangement, serving as examples.

The microphone consists of a round cylindrical carbon disk K, Fig. 3, in the portion of which that faces the diaphragm 7. are arranged cavities 0, (here seven in number,) in

other elm-tic material, for keeping the granular carbon in a loose condition. The carbon disk K is fastened to the metal casing of the microphone by means of the screw to, passing through the central one of the cavities 0. Around the said carbon disk K is placed a ring R of felting, cloth, or other elastic material. The ring is pressed against the carbon diaphragm k by means of thespringing.

R. thus serves both to retain the granulated carbon in its place and to exert an even constant pressure on the diaphragm during its vibrations. By this arrangement a good articulation is effected, and at the same time the sound will not be disagreeable to the car even when the speech in the microphone is loud or screeching. r

In order to protect the interior parts of the microphone from dampness and dust, a waterproof membrane S of impregnated silk or other suitable material is located in front of the carbon diaphragm it.

Having now described my invention,-what I claim as new, and desire to secure by Letters Patent, is i In combination, in a microphone, a disk, a ring of elastic material surrounding the same and projecting beyond the face thereof, a diaphragm opposite the disk, carbon granules in the space bounded by the elastic ring the disk and the diaphragm, and the spring for pressing the elastic ring toward the diaphragm,

substantially as described.

In witness whereof I have hereunto signed my name inthe presence of two subscribing which, as previously known, are placed small 1 cylinders, made of felting, cloth, or some witnesses.

LABS MAGNUS ERIOSSON. Witnesses:

IEDER HAMMARSHJOLT), r1. 0. iu nnnnu. 

